Along with EC 3.5.1.54 (allophanate hydrolase) and EC 3.5.1.84 (biuret amidohydrolase), this enzyme forms part of the cyanuric-acid metabolism pathway, which degrades s-triazide herbicides, such as atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-1,3,5-triazine], in bacteria. This is a key enzyme in the pathway, catalysing the ring cleavage of cyanuric acid. The enzyme is specific for cyanuric acid as substrate as neither the structurally related compounds ammeline (2,4-diamino-6-hydroxy-s-triazine) and ammelide (2-amino-4,6-dihydroxy-s-triazine) nor a number of pyrimidine compounds, such as uracil and cytosine, can act as substrates [3].